Bimetallic NiMnOx catalysts enable cascade C–H and C–C bond cleavage for efficient low-temperature ethane oxidation

Abstract

Transition metal oxide catalysts offer a cost-effective and efficient alternative to noble metal catalysts for the environmental treatment of light alkane pollutants. In this study, a bimetallic Ni_0.2Mn_0.8O_x catalyst was evaluated for its effectiveness in the low-temperature catalytic oxidation of ethane, which achieved an ethane conversion of 90 % at only 286 °C and exceeded 99 % at 325 °C. Under conditions of poisoning with 5 vol% H₂O or 10 ppm H₂S for 10 h, the activity of the Ni_0.2Mn_0.8O_x catalyst remained essentially unchanged. The characterization results indicated that the Ni sites on the surface of Ni_0.2Mn_0.8O_x were favorable for the adsorption of ethane. Simultaneously introducing Ni promoted lattice distortion in MnO_x and increased the exposure of lattice oxygen to participate in the reaction. In mechanistic studies, it was elucidated that the Ni sites play a distinct role in facilitating the scission of C–H bonds, while the Mn sites exhibit a specific propensity towards breaking C–C bonds. The synergistic effect between Ni and Mn sites promoted the activation of ethane on the surface of Ni_0.2Mn_0.8O_x and decomposing into H₂O and CO₂ under the function of lattice oxygen. The monolithic catalysts demonstrated long-term stability, maintaining removal rates of ethane above 85 % under dry conditions and 75 % under wet conditions for up to 100 h. This performance suggests significant potential for industrial applications.